A review: Energy recovery in batch processes

The implementation of batch processing has increased due to its intrinsic flexibility and adaptability. These are essential characteristics when it comes to producing high-value added materials such as agrochemicals, pharmaceuticals, specialty chemicals…the demand for which has grown in recent decades.Although industrial processes are highly diverse, a common feature to all is that they utilize fossil fuels as the energy source. The reliance on fossil fuels as a primary source of energy generates a negative impact on the environment. The implantation of renewable energies and efficient usage of energy has thus become crucial. Improving energy use could be achieved through advancements in plant machinery and the use of methodologies such as ‘process integration’.Process integration can be described as system oriented methods that could be used during the design and retrofit of industrial processes in order to obtain an optimal utilization of resources. The methods have traditionally focused on an efficient energy use, although recently process integration techniques cover other areas such as efficient use of raw materials, emission reduction and process operations. Energy integration tries to reach the optimization of heat, power, fuel and utilities.The consideration of energy integration complicates the process design and the generation of batch process design alternatives, so what is now required is the proposal and development of different approaches and methods oriented towards recovering energy in this kind of industrial process. Improving energy end-use efficiency will make it possible to reduce dependence on energy imports and bring about innovation and competitiveness.The aim of this work is report the main contributions that have been carried out in order to attain energy integration in batch processes, as well as different examples of applications that have shown the possibilities offered by the developed tools.     

Modeling the operation of hydrogen supply networks considering facility location

Hydrogen draws increasing attention as an alternative energy source. In order to provide hydrogen to various sectors such as industry, transportation on a global scale, how to produce and distribute it economically is an essential issue not to be missed. This study thereby addresses mathematical modeling of hydrogen supply networks. The proposed model is concerned with how much H₂ can be produced, where can be stored with the aim of maximizing the total net profit. Particularly the physical form of the hydrogen in the network is explicitly taken into account in terms of whether it is stored as a gas or a liquid. The applicability of the proposed model will be demonstrated by a case study of the Korean H₂ supply network with some remarks.     

柔性电动汽车和分布式电源的协同优化调度研究

针对电动汽车(EV)接入电网后,出现的负荷"峰上加峰"的问题,在描述传统机组发电特征及调度分布式电源作为补充的基础上,提出了柔性电动汽车与分布式电源协同优化调度方案。该方案考虑4类电动汽车的出行规律及充电方式,同时以发电投资总成本与柔性EV用能成本之和最小作为优化目标,建立车网交互(V2G)的机组组合模型。在考虑柔性EV行驶特性与机组运行特性基础上,将所提模型转化为一个大规模混合整数线性规划(MILP)问题,利用Ipsolve解算器求得最优解以及最优调度方案。文章选取某城市各类电动汽车为研究对象,分析柔性EV用能成本对系统总成本与CO2排放量的影响。仿真结果验证了采用柔性EV与风电协同优化传统机组出力的有效性和考虑柔性EV用能成本的必要性。     

A MILP model for integrated plan and evaluation of distributed energy systems

In the last decade, technological innovations and a changing economic and regulatory environment have resulted in a renewed interest for distributed energy resources (DER). However, because of the lack of a suitable design tool, the expected potential of DER penetration is not always exerted sufficiently. In this paper, a mixed-integer linear programming (MILP) model has been developed for the integrated plan and evaluation of DER systems. Given the site’s energy loads, local climate data, utility tariff structure, and information (both technical and financial) on candidate DER technologies, the model minimizes overall energy cost for a test year by selecting the units to install and determining their operating schedules. Furthermore, the economic, energetic and environmental effects of the DER system can be evaluated. As an illustrative example, an investigation has been conducted of economically optimal DER system for an eco-campus in Kitakyushu, Japan. The result illustrates that gas engine is currently the most popular DER technology from the economic point of view. Although holding reasonable economic merits, unless combined with heat recovery units, the introduction of DER technologies may result in marginal or even adverse environmental effects. Furthermore, according to the results of sensitivity analysis, the optimal system combination and corresponding economic and environmental performances are more or less sensitive to the scale of energy demand, energy prices (both electricity and city gas), as well as carbon tax rate.     

Control structure selection for energy integrated distillation column

This paper treats a case study on control structure selection for an almost binary distillation column. The column is energy integrated with a heat pump in order to transfer heat from the condenser to the reboiler. This integrated plant configuration renders the possible control structures somewhat different from what is usual for binary distillation columns. Further the heat pump enables disturbances to propagate faster through the system. The plant has six possible actuators of which three must be used to stabilize the system. Hereby three actuators are left for product purity control. An MILP screening method based on a linear state space model is used to determine economically optimal sets of controlled and manipulated variables. The generated sets of inputs and outputs are analysed with frequency dependent relative gain array (RGA), relative disturbance gain (RDG) and condition number (CN) to determine the best structure in terms disturbance rejection and setpoint tracking. The pairing and controller design are implemented and evaluated through nonlinear simulation. The suggested control structure is also qualitatively compared to a control structure applied experimentally.     

Solving discretely constrained,mixed linear complementarity problems with applications in energy

This paper presents an approach to solving discretely constrained, mixed linear complementarity problems (DC-MLCPs). Such formulations include a variety of interesting and realistic models of which two are highlighted: a market-clearing auction typical in electric power markets but suitable in other more general contexts, and a network equilibrium suitable to energy markets as well as other grid-based industries. A mixed-integer, linear program is used to solve the DC-MLCP in which both complementarity as well as integrality are allowed to be relaxed. Theoretical and numerical results are provided to validate the approach.     

基于混合整数线性规划的风电场有功优化调度

大规模风电并网背景下,风电场的有功优化调度对调度控制和电网安全运行至关重要。在风电场风速分布和风电功率有效评估的基础上,以风电机组的出力以及开停机状态为决策变量,考虑风电场弃风以及机组启停,建立了以风电场运行成本最低为目标的风电场优化调度模型。提出了风能利用系数的分段线性化方法,进而建立了基于混合整数线性规划的风电场优化调度模型。实际风电场的算例分析表明,该调度模型可在满足调度部门指令需求的前提下,给出风电场内最优的机组启停计划和出力安排,有效减少弃风及启停次数,降低风电场运行成本。     

基于WARD等值的电网限流运行方式优化方法

控制短路电流水平,保证断路器安全是电网运行方式安排的重要任务。线路开断及母线分裂以增大变电站母线与电源之间的电气距离是限制电网短路电流水平的有效措施,但同时也可能引起电网运行可靠性水平的降低。首先根据对网络拓扑结构的分析及线路开断前后超标站点的短路电流变化确定可开断支路集;然后添加功率平衡方程约束、支路潮流约束以及N-1安全约束;以开断线路数最少为目标,提出了控制短路电流水平的电网运行方式优化模型,并借助WARD等值缩小模型规模,提高了模型的求解效率。所提模型为混合整数线性规划模型,可以采用线性规划单纯形法及分支定界法迅速求解。使用C++编写了仿真程序,通过对IEEE39节点系统和某实际电网的仿真分析验证了所提模型的正确性和算法的有效性。